(CNN) -- An international youth camp in western Norway is being shut down after swine flu broke out among the teenagers, the organizers, 4H Norway, announced Saturday.

Of the 1,700 participants, 37 have developed symptoms of swine flu and are now in isolation in the town of Gloppen. No one is seriously ill, however, and no one has been hospitalized, a source in the Norwegian Directorate of Health told CNN.

All of those affected had traveled to the youth camp in the same bus.

"People are mostly sad that they have to go home now since they have been preparing for this camp for so long," Astrid Solberg, secretary-general of 4H, told CNN.

Children from 15 countries are at the camp, which was supposed to end next Wednesday.